1. Field of the Invention
The present invention relates to a writing instrument such as a correction liquid marker, a paint marker and the like, and more particularly to a writing instrument which can stir in the ink passage ink which is being supplied from the ink reservoir to the nib.
2. Description of the Related Art
More particularly, the present invention relates to an improvement of a writing instrument which compresses air in a cap to be forced into the main body when the cap is mounted on the main body so that ink is supplied to the nib under the pressure of the compressed air.
various kinds of correction liquid markers have recently developed for applying correction liquid to required portions. These developed correction liquid markers have the advantages that they can be used more conveniently than the conventional ones and they can be applied to narrow portions with clear contour.
FIG. 1 shows a conventional correction liquid marker. A main body 1 is cylindrical and contains an ink reservoir 2 which is filled with correction ink or correction liquid. To the front end of the main body 1 is connected a nib holder 5 whose front end portion holds a nib portion such as a ball tip 3. The front end of the ball tip 3 holds a ball 4 having a relatively large diameter. An ink passage 8 extends through the nib holder 5 and the ball tip 3 and connects the ink reservoir 8 to the interior of the ball tip 3. A spring 6 is provided in the ink passage 8. A push rod 7 made of a piano wire, for example, extends to the ball 4 from an end of the spring 6 which is remote from the ink reservoir 2. The free front end of the push rod 7 abuts against the ball 3 so that the ball 4 is urged forward to close the ball tip 3.
A cap 9 is slidably fitted in an air tight manner on the front end portion of the nib holder 5. Upon fitting the cap 9 on the nib holder 5, air in the cap 9 is compressed and is pushed in the ink reservoir 2 through the ink passage 3.
Stirring weights 10 such as steel balls are provided in the ink reservoir 2 and are moved therein by swinging the correction liquid marker.
The correction liquid marker of this type is usually called a cap compression type writing instrument. Every time the cap 9 is fitted on the nib holder, air is introduced under pressure in the ink reservoir 2, thereby permanently maintaining a predetermined pressure in the ink reservoir 2. Since the ball 4 is urged forward by the spring 6 and the push rod 7 and by the pressure in the ink reservoir 2 as well, the ball tip 3 is closed by the ball 4 to prevent correction liquid from flowing out from the correction liquid marker when the marker is not in use.
Upon using the marker, the ball 4 is retracted slightly by the pressure applied by the marker against the urging forces by the spring 6 and the internal pressure of the ink in the ink reservoir 2. The ball 4 is released from the ball tip 3 and the correction liquid under the pressure in the ink reservoir 2 flows out. Rolling of the ball 4 by use of the marker allows correction liquid to be applied to the required portion. The correction liquid has a disadvantage that pigment contained in the correction liquid is likely to be deposited. The conventional correction liquid marker is constructed so that the stirring weights 10 are provided in the ink reservoir 2 and the correction liquid is stirred by moving them in the ink reservoir 2. However, the correction liquid between the ink reservoir 2 and the ball 4 in the ball tip 3 cannot be stirred by the stirring weights 8. Pigment in the correction liquid in the ink passage 8 is deposited, and the correction liquid in which the pigment is sometimes deposited is supplied at the initial stage of the use of the marker. Further, air is likely to be accumulated in the ink passage 8. Thus, air in the ink passage 8 is not removed from the ink passage 8, even if the correction liquid in the ink reservoir 2 is stirred by swinging the correction liquid marker. In this regard, the correction liquid sometimes becomes blurred by the air in the ink passage 8 at the beginning of use of the marker.
When the cap 9 is fitted on the nib holder 5, air in the cap 9 to be pushed in the correction liquid marker is compressed and retracts the ball 4 against the urging force of the spring 6. The urging force of the spring 6 must be somewhat large so as to close the ink passage 8 securely. Upon fitting the cap 9 on the nib holder 5, therefore, the air under pressure in the cap 9 is sometimes not pushed in the correction liquid marker fully.
when the cap 9 is mounted on the nib holder 5 in the marker of a cap compression type, air compressed in the cap 9 retracts the ball 4 in the ball tip 3 and enters the ink reservoir 2 under pressure. The pressure in the cap 9 and the pressure in the ink reservoir 2 gradually become in equilibrium with each other, and the amount of air entering the ink reservoir 5 through the ball tip 3 gradually decreases. The air compressed into the ink passage 8 or the ink reservoir 2 is initially diffused in the ink as air bubbles. But it is gathered to form large air bubbles and is finally separated from the ink to be changed into the gaseous phase in the ink reservoir 2. However, as the pressures in the cap 9 and the ink reservoir 2 become in equilibrium with each other and the flowing amount of the air is reduced as described above, the compressed air is changed into extremely fine air bubbles and is diffused in the ink. The ink containing the extremely fine air bubbles has apparently high viscosity. The very fine air bubbles are not gathered together easily, and ink containing the very fine air bubbles remains in the ink passage 8 for a long time. Since the contact area with the air bubbles, i.e., air is very large, the ink in this state is solidified as time passes, and the viscosity becomes larger, whereby the ink passage 8 clogs with the ink. This phenomenon occurs to ink easily when the ink is correction liquid, but it sometimes occurs to any other ink.
As described above, the problems occurring to the conventional writing instruments were described by way of a correction liquid marker. However, the paint marker, and any other writing instrument having the same structure as the correction liquid marker, have encountered the same problems.